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Documentation / devicetree / bindings / arm / psci.txt




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Based on kernel version 3.16. Page generated on 2014-08-06 21:36 EST.

1	* Power State Coordination Interface (PSCI)
2	
3	Firmware implementing the PSCI functions described in ARM document number
4	ARM DEN 0022A ("Power State Coordination Interface System Software on ARM
5	processors") can be used by Linux to initiate various CPU-centric power
6	operations.
7	
8	Issue A of the specification describes functions for CPU suspend, hotplug
9	and migration of secure software.
10	
11	Functions are invoked by trapping to the privilege level of the PSCI
12	firmware (specified as part of the binding below) and passing arguments
13	in a manner similar to that specified by AAPCS:
14	
15		 r0		=> 32-bit Function ID / return value
16		{r1 - r3}	=> Parameters
17	
18	Note that the immediate field of the trapping instruction must be set
19	to #0.
20	
21	
22	Main node required properties:
23	
24	 - compatible    : should contain at least one of:
25	
26					 * "arm,psci" : for implementations complying to PSCI versions prior to
27						0.2. For these cases function IDs must be provided.
28	
29					 * "arm,psci-0.2" : for implementations complying to PSCI 0.2. Function
30						IDs are not required and should be ignored by an OS with PSCI 0.2
31						support, but are permitted to be present for compatibility with
32						existing software when "arm,psci" is later in the compatible list.
33	
34	 - method        : The method of calling the PSCI firmware. Permitted
35	                   values are:
36	
37	                   "smc" : SMC #0, with the register assignments specified
38			           in this binding.
39	
40	                   "hvc" : HVC #0, with the register assignments specified
41			           in this binding.
42	
43	Main node optional properties:
44	
45	 - cpu_suspend   : Function ID for CPU_SUSPEND operation
46	
47	 - cpu_off       : Function ID for CPU_OFF operation
48	
49	 - cpu_on        : Function ID for CPU_ON operation
50	
51	 - migrate       : Function ID for MIGRATE operation
52	
53	
54	Example:
55	
56	Case 1: PSCI v0.1 only.
57	
58		psci {
59			compatible	= "arm,psci";
60			method		= "smc";
61			cpu_suspend	= <0x95c10000>;
62			cpu_off		= <0x95c10001>;
63			cpu_on		= <0x95c10002>;
64			migrate		= <0x95c10003>;
65		};
66	
67	
68	Case 2: PSCI v0.2 only
69	
70		psci {
71			compatible	= "arm,psci-0.2";
72			method		= "smc";
73		};
74	
75	Case 3: PSCI v0.2 and PSCI v0.1.
76	
77		A DTB may provide IDs for use by kernels without PSCI 0.2 support,
78		enabling firmware and hypervisors to support existing and new kernels.
79		These IDs will be ignored by kernels with PSCI 0.2 support, which will
80		use the standard PSCI 0.2 IDs exclusively.
81	
82		psci {
83			compatible = "arm,psci-0.2", "arm,psci";
84			method = "hvc";
85	
86			cpu_on = < arbitrary value >;
87			cpu_off = < arbitrary value >;
88	
89			...
90		};
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